Aortic stenosis

 

Disease:

Causes

1.    Degenerative – old

2.    Congenital (bileaflet) – young

3.    Rheumatic – indigenous or third world

Natural history

·      Progressive deterioration

·      Minimal increase in gradient until 50% loss of area

Annual changes:

·      Velocity ↑0.3m/s

·      AVA ↓0.1cm2

·      Grad ↑4-7mmHg

Time to 50% mortality:

·      Angina: 5y

·      Syncope: 3y

·      Dyspnoea: 2y (i.e. LV failure)

Classic teaching:

·      High mortality if severe and symptomatic

·      Low mortality if severe but asymptomatic

New teaching:

·      High mortality even if moderate (56% at 5 years)

·      Replace if severe / symptomatic / LV impairment   (?)

Secondary effects

·      Diastolic dysfunction

·      Systolic dysfunction

·      Myocardial ischaemia

·      Pulmonary hypertension

Associations

·      Ischaemic heart disease

·      Other valve disease (esp if rheumatic)

·      Acquired vWD (shear forces -> consumption)

·      Mucosal and gastrointestinal angiodysplasias

Differentials

-Systolic murmur

Common:

·      MR

·      HCM

Uncommon:

·      PS

·      TR

·      VSD

Treatment

·      Balloon (esp bridging)

·      TAVR

·      SAVR

 

Presentation:

Significance

·      Poor correlation with severity of disease

History

·      Angina

·      Syncope

·      Dyspnoea

Examination

Aortic stenosis:

·      Small volume, slow-rising pulse

·      Hyperdynamic, displaced apex beat

·      Harsh ESM at RUSB -> carotid, ± thrill

Severe disease:

·      Weak pulse

·      Late-peaking murmur

·      Thrill

·      Soft S2

ECG

·      LVH (high voltage)

·      Strain (ST depression + T wave inversion)

 

Echo:

Suggestive

·      PLAx and PSAx views

·      Thickened and restricted

·      Abnormal number of leaflets

Diagnostic

PSAX view:

·      Number of leaflets

·      Appearance of restriction

·      Presence of regurgitation

PLAX view:

·      Velocity:

o  CWD through LVOT

·      Mean gradient:

o  Simplified Bernoulli equation (∆P = 4v2)

o  Usually greater than LHC pull-back gradient

·      Valve area:

o  Conservation of mass

o  VTILVOT x areaLVOT = VTIAV x areaAV

·      Velocity ratio = dimensionless index

o  LVOT VTI : AV VTI

o  <0.25 indicates severe disease

o  Important in low flow, low gradient AS

Complications

·      LVH: ↑wall thickness

·      LA enlargement: ↑diameter

·      Diastolic dysfunction: A4C view – abnormal E/A, ↑E/E’

·      Systolic dysfx: PLAx and PSAx views – reduced motion

·      PHTN: A4C view – CWD at TR jet > 2.8m/s

 

Grading:

 

 

 

Mild

Moderate

Severe

Velocity

2-3

3-4

>4

Mean gradient

5-20

20-40

>40

Valve area

1.5-2.5

1-1.5

<1

Dimensionless index

0.5-1

0.25-0.5

<0.25

 

Anaesthesia issues:

Death spiral

Ischaemia risk

·      ↑Demand: hypertrophy + pressure work

·      ↓Supply: if hypotension (common in anaesthesia)

Low cardiac output

·      Dependent on SVR for mAP

Fixed cardiac output

·      Dependent on HR for CO

Diastolic dysfunction

·      Dependent on preload, but also risk of pulmonary congestion

·      Dependent on sinus rhythm

Pulmonary HTN

·      See other document

·      Maintain coronary perfusion

·      Minimise afterload i.e. PVR

 

Anaesthesia management:

Goals

·      Full: euvolaemia for preload

·      Slow: normal HR for filling time, sinus rhythm for atrial kick

·      Tight: maintain SVR hence mAP hence coronary perfusion

Access

·      Arterial line pre-induction

·      Large IV + pumpset

·      ±CVC if impaired systolic function

Monitoring

·      Standard

·      5 lead ECG

·      Arterial line

·      PPV

Induction drugs

·      Don’t do a spinal

·      CSL 250mL bolus

·      Metaraminol infusion 10mg/h

·      Fentanyl 5mcg/kg

·      Propofol 1-2mg/kg very slowly until LOC

·      Rocuronium 0.6mg/kg at LOC

 

 

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